Kinetic suspension system with comfort valve integration

ABSTRACT

A suspension system including four dampers is disclosed where each damper includes a compression chamber and a rebound chamber. A first hydraulic circuit includes a front hydraulic line, a rear hydraulic line, and a first longitudinal hydraulic line that extends between and fluidly connects the front and rear hydraulic lines of the first hydraulic circuit. A second hydraulic circuit includes a front hydraulic line, a rear hydraulic line, and a second longitudinal hydraulic line that extends between and fluidly connects the front and rear hydraulic lines of the second hydraulic circuit. First and second longitudinal comfort valves are positioned in the first and second longitudinal hydraulic lines, respectively, between the front and rear hydraulic lines. Both of the first and second longitudinal comfort valves are electromechanical valves and can be actuated to couple and decouple front axle roll control from rear axle roll control.

FIELD

The present disclosure relates generally to suspension systems for motor vehicles and more particularly to suspension systems that resist the roll movements of a vehicle.

BACKGROUND

The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

Suspension systems improve the ride of a vehicle by absorbing bumps and vibrations that would otherwise unsettle the vehicle body. Suspension systems also improve safety and control by improving contact between the ground and the tires of the vehicle. One drawback of suspension systems is that basic spring/damper arrangements will allow the vehicle to roll/lean right or left during corning (e.g., in turns), pitch forward under deceleration (e.g., under braking), and pitch back under acceleration. The lateral acceleration the vehicle experiences in turns causes a roll moment where the vehicle will lean/squat to the right when turning left and to the left when turning right. The fore and aft acceleration the vehicle experiences under acceleration and braking causes a pitch moment where the vehicle will lean forward loading the front axle during braking and aft, loading the rear axle, under acceleration. These roll and pitch moments decrease grip, cornering performance, and braking performance and can also be uncomfortable to the driver and passengers. Many vehicles are equipped with stabilizer bars/anti-roll bars, which are mechanical systems that help counteract the roll moments experienced during driving. For example, anti-roll bars are typically mechanical linkages that extend laterally across the width of the vehicle between the right and left dampers. When one of the dampers extends, the anti-roll bar applies a force to the opposite damper that counteracts the roll moment of the vehicle and helps to correct the roll angle to provide flatter cornering. However, there are several draw backs associated with these mechanical systems. First, there are often packaging constraints associated with mechanical systems because a stabilizer bar/anti-roll bar requires a relatively straight, unobstructed path across the vehicle between the dampers. Second, stabilizer bars/anti-roll bars are reactive and work when the suspension starts moving (i.e. leaning). Such mechanical systems cannot be easily switched off or cancelled out when roll stiffness is not need. Some vehicles do have stabilizer bar/anti-roll bar disconnects that may be manually or electronically actuated, but the complexity and cost associated with these systems make them ill-suited for most vehicle applications.

In an effort to augment or replace traditional mechanical stabilizer bars/anti-roll bars, anti-roll suspension systems are being developed that hydraulically connect two or more dampers in a hydraulic circuit where the extension of one damper produces a pressure change in the other damper(s) in the hydraulic circuit that makes it more difficult to compress the other damper(s) in the hydraulic circuit. This pressure change in the other damper(s) increases the roll stiffness of the suspension system of the vehicle. However, the downside of such systems is that ride comfort is more difficult to achieve because bump forces can be transmitted from one damper to another damper across the hydraulic circuit resulting in unwanted suspension movement. Accordingly, there remains a need for improved vehicle suspension systems that can minimize roll while maintaining acceptable levels of ride comfort.

SUMMARY

This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.

In accordance with one aspect of the subject disclosure, a suspension system is provided that includes four dampers: a front left damper, a front right damper, a back left damper, and a back right damper. The front left damper includes a first compression chamber and a first rebound chamber. The front right damper includes a second compression chamber and a second rebound chamber. The back left damper includes a third compression chamber and a third rebound chamber. The back right damper includes a fourth compression chamber and a fourth rebound chamber. The suspension system of the present disclosure also includes first and second hydraulic circuits.

The first hydraulic circuit includes a front hydraulic line, a rear hydraulic line, and a first longitudinal hydraulic line that extends between and fluidly connects the front and rear hydraulic lines of the first hydraulic circuit. The front hydraulic line of the first hydraulic circuit extends between and fluidly connects the first longitudinal hydraulic line and the second rebound chamber of the front right damper. The rear hydraulic line of the first hydraulic circuit extends between and fluidly connects the first longitudinal hydraulic line and the fourth rebound chamber of the back right damper. The first longitudinal hydraulic line extends between and fluidly connects the first compression chamber of the front left damper and the third compression chamber of the back left damper.

The second hydraulic circuit includes a front hydraulic line, a rear hydraulic line, and a second longitudinal hydraulic line that extends between and fluidly connects the front and rear hydraulic lines of the second hydraulic circuit. The front hydraulic line of the second hydraulic circuit extends between and fluidly connects the second longitudinal hydraulic line and the first rebound chamber of the front left damper. The rear hydraulic line of the second hydraulic circuit extends between and fluidly connects the second longitudinal hydraulic line and the third rebound chamber of the back left damper. The second longitudinal hydraulic line extends between and fluidly connects the second compression chamber of the front right damper and the fourth compression chamber of the back right damper.

The suspension system further includes first and second longitudinal comfort valves. The first longitudinal comfort valve is positioned in the first longitudinal hydraulic line between the front and rear hydraulic lines of the first hydraulic circuit. The second longitudinal comfort valve is positioned in the second longitudinal hydraulic line between the front and rear hydraulic lines of the second hydraulic circuit. Both of the first and second longitudinal comfort valves are electromechanical valves.

Advantageously, the suspension system of the present disclosure is able to reduce/eliminate vehicle roll while cornering for improved grip, performance, handling, and braking. The reduction of roll angles improves the comfort, steering feel, agility, and stability of the vehicle. Roll control is provided by increasing the roll stiffness of the suspension system (based on static pressure in the system). The level of roll stiffness can be adjusted by using a pump to change the static pressure in select hydraulic circuits of the system. The first and second longitudinal comfort valves can be closed to decouple the front and rear dampers in each of the first and second hydraulic circuits in situations where different levels of roll stiffness are desired for the front and rear axles.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages of the present disclosure will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is a schematic diagram illustrating an exemplary suspension system of the present disclosure that includes two comfort valves that open and close the hydraulic lines connecting the two front dampers to the two rear dampers of the system;

FIG. 2 is a schematic diagram illustrating another exemplary suspension system of the present disclosure that includes two comfort valves that open and close the hydraulic lines connecting the two front dampers to the two rear dampers of the system and a separate hydraulic lifting circuit for the two front dampers;

FIG. 3 is a schematic diagram illustrating another exemplary suspension system of the present disclosure that includes two comfort valves that open and close the hydraulic lines connecting the two front dampers to the two rear dampers of the system and two separate hydraulic lifting circuits for the two front dampers and the two rear dampers;

FIG. 4 is a schematic diagram illustrating another exemplary suspension system of the present disclosure that includes four hydraulic circuits connecting the front and rear dampers and an exemplary comfort valve equipped manifold assembly;

FIG. 5 is a schematic diagram illustrating the exemplary comfort valve equipped manifold assembly illustrated in FIG. 4 ;

FIG. 6 is a schematic diagram illustrating another exemplary suspension system of the present disclosure that includes four hydraulic circuits connecting the front and rear dampers and another exemplary comfort valve equipped manifold assembly; and

FIG. 7 is a schematic diagram illustrating another exemplary suspension system of the present disclosure that includes four hydraulic circuits connecting the front and rear dampers and another exemplary comfort valve equipped manifold assembly.

DETAILED DESCRIPTION

Referring to the Figures, wherein like numerals indicate corresponding parts throughout the several views, various comfort valve equipped suspension systems are shown.

Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed.

When an element or layer is referred to as being “on,” “engaged to,” “connected to,” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to,” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments.

Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

With reference to FIG. 1 , a suspension system 100 including a front left damper 102 a, a front right damper 102 b, a back left damper 102 c, and a back right damper 102 d. While it should be appreciated that the suspension system 100 described herein may include a different number of dampers than those shown in the drawings, in most automotive applications, four dampers are used at each corner of a vehicle to control vertical movements of the front and rear wheels of the vehicle. Thus, the front left damper 102 a controls (e.g., dampens) up and down (i.e., vertical) movements of the front left wheel of the vehicle, the front right damper 102 b controls (e.g., dampens) up and down (i.e., vertical) movements of the front right wheel of the vehicle, the back left damper 102 c controls (e.g., dampens) up and down (i.e., vertical) movements of the back left wheel of the vehicle, and the back right damper 102 d controls (e.g., dampens) up and down (i.e., vertical) movements of the back right wheel of the vehicle.

The suspension system 100 also includes a manifold assembly 104 that is connected in fluid communication with a pump assembly 106 by a pump hydraulic line 108. Although other configurations are possible, in the illustrated example, the pump assembly 106 includes a bi-directional pump 110, a hydraulic reservoir 112 (e.g., a tank), and a bypass hydraulic line 114 that can be open and closed by a pressure relief valve 116. The bi-directional pump 110 includes a first inlet/outlet port that is connected to the pump hydraulic line 108 and a second inlet/outlet port that is connected in fluid communication with the hydraulic reservoir 112 by a reservoir hydraulic line 118. The bi-directional pump 110 may operate (i.e., pump fluid) in two opposite directions depending on the polarity of the electricity that is supplied to the pump 110, so the first inlet/outlet port may operate as either an inlet port or an outlet port depending on the direction the bi-directional pump 110 is operating in and the same is true for the second inlet/outlet port of the bi-directional pump 110. In the example where the first inlet/outlet port is operating as an inlet port for the bi-directional pump 110 and the second inlet/outlet port is operating as an outlet port for the bi-directional pump 110, the bi-directional pump 110 draws in hydraulic fluid from the pump hydraulic line 108 via the first inlet/outlet port and discharges hydraulic fluid into the reservoir hydraulic line 118 via the second inlet/outlet port. As such, the bi-directional pump 110 produces a negative pressure in the pump hydraulic line 108 that can be used by manifold assembly 104 to reduced fluid pressure in the suspension system 100. In the example where the second inlet/outlet port is operating as an inlet port for the bi-directional pump 110 and the first inlet/outlet port is operating as an outlet port for the bi-directional pump 110, the bi-directional pump 110 draws in hydraulic fluid from the reservoir hydraulic line 118 via the second inlet/outlet port and discharges hydraulic fluid into the pump hydraulic line 108 via the first inlet/outlet port. As such, the bi-directional pump 110 produces a positive pressure in the pump hydraulic line 108 that can be used by manifold assembly 104 to increase fluid pressure in the suspension system 100. The bypass hydraulic line 114 runs from the pump hydraulic line 108 to the hydraulic reservoir 112 and bleeds fluid back into the hydraulic reservoir 112 when the pressure in the pump hydraulic line 108 exceeds a threshold pressure that causes the pressure relief valve 116 to open.

The manifold assembly 104 is connected in fluid communication with the front and rear dampers 102 a, 102 b, 102 c, 102 d by first and second hydraulic circuits 120 a, 120 b. The manifold assembly 104 includes first and second manifold valves 122 a, 122 b that are connected in parallel with the pump hydraulic line 108. The first hydraulic circuit 120 a is connected in fluid communication with the first manifold valve 122 a and the second hydraulic circuit 120 b is connected in fluid communication with the second manifold valve 122 b. The manifold assembly 104 also includes a first pressure sensor 124 a that is arranged to monitor the pressure in the first hydraulic circuit 120 a and a second pressure sensor 124 b that is arranged to monitor the pressure in the second hydraulic circuit 120 b. The bi-directional pump 110 of the pump assembly 106 and first and second pressure sensors 124 a, 124 b and the first and second manifold valves 122 a, 122 b of the manifold assembly 104 are electrically connected to a controller (not shown), which is configured to activate (i.e., turn on in forward or reverse) the bi-directional pump 110 and electronically actuate (i.e., open and close) the first and second manifold valves 122 a, 122 b in response to various inputs, including signals from the first and second pressure sensors 124 a, 124 b. When the controller opens the first and second manifold valves 122 a, 122 b, the fluid pressure in the first and second hydraulic circuits 120 a, 120 b increases or decreases depending on which direction the bi-directional pump 110 is running in.

The anti-roll capabilities of the suspension system 100 will be explained in greater detail below; however, from FIG. 1 it should be appreciated that fluid pressure in the first and second hydraulic circuits 120 a, 120 b operate to dynamically adjust the roll stiffness of the vehicle and can be used to either augment or completely replace mechanical stabilizer bars/anti-roll bars. Such mechanical systems require relatively straight, unobstructed runs between each of the front dampers 102 a, 102 b and each of the back dampers 102 c, 102 d. Accordingly, the suspension system 100 disclosed herein offers packaging benefits because the dampers 102 a, 102 b, 102 c, 102 d only need to be hydraulically connected to the manifold assembly 104.

Each of the dampers 102 a, 102 b, 102 c, 102 d of the suspension system 100 includes a damper housing, a piston rod, and a piston that is mounted on the piston rod. The piston is arranged in sliding engagement with the inside of the damper housing such that the piston divides the damper housing into compression and rebound chambers. As such, the front left damper 102 a includes a first compression chamber 126 a and a first rebound chamber 128 a, the front right damper 102 b includes a second compression chamber 126 b and a second rebound chamber 128 b, the back left damper 102 c includes a third compression chamber 126 c and a third rebound chamber 128 c, and the back right damper 102 d includes a fourth compression chamber 126 d and a fourth rebound chamber 128 d.

In each damper 102 a, 102 b, 102 c, 102 d, the piston is a closed piston with no fluid flow paths defined within or by its structure. In addition, there are no other fluid flow paths in the damper housing such that no fluid is communicated between the compression and rebound chambers of the dampers 102 a, 102 b, 102 c, 102 d except through the first and second hydraulic circuits 120 a, 120 b. The rebound chambers 128 a, 128 b, 128 c, 128 d of the dampers 102 a, 102 b, 102 c, 102 d decrease in volume during rebound/extension strokes and increase in volume during compression strokes of the dampers 102 a, 102 b, 102 c, 102 d. The compression chambers 126 a, 126 b, 126 c, 126 d of the dampers 102 a, 102 b, 102 c, 102 d decrease in volume during compression strokes of the dampers 102 a, 102 b, 102 c, 102 d and increase in volume during rebound/extension strokes of the dampers 102 a, 102 b, 102 c, 102 d.

Each damper 102 a, 102 b, 102 c, 102 d also includes rebound and compression chamber ports 130 a, 130 b in the damper housing that are each provided with dampening valves. The rebound chamber port 130 a is arranged in fluid communication with the rebound chamber 128 a, 128 b, 128 c, 128 d of the damper 102 a, 102 b, 102 c, 102 d and the second port 130 b is arranged in fluid communication with the compression chamber 126 a, 126 b, 126 c, 126 d of the damper 102 a, 102 b, 102 c, 102 d. The dampening valves in the rebound and compression chamber ports 130 a, 130 b can be passive/spring-biased valves (e.g., spring-disc stacks) or active valves (e.g., electromechanical valves) and control fluid flow into and out of the compression and rebound chambers of the dampers 102 a, 102 b, 102 c, 102 d to provide one or more rebound dampening rates and compression dampening rates for each of the dampers 102 a, 102 b, 102 c, 102 d.

The first hydraulic circuit 120 a includes a first longitudinal hydraulic line 132 a that extends between and fluidly connects the second port 130 b (to the first compression chamber 126 a) of the front left damper 102 a and the second port 130 b (to the third compression chamber 126 c) of the back left damper 102 c. The first hydraulic circuit 120 a includes a front hydraulic line 134 a that extends between and fluidly connects the first longitudinal hydraulic line 132 a and the rebound chamber port 130 a (to the second rebound chamber 128 b) of the front right damper 102 b. The first hydraulic circuit 120 a also includes a rear hydraulic line 136 a that extends between and fluidly connects the first longitudinal hydraulic line 132 a and the rebound chamber port 130 a (to the fourth rebound chamber 128 d) of the back right damper 102 d. The first hydraulic circuit 120 a further includes a first manifold hydraulic line 138 a that extends between and fluidly connects the first longitudinal hydraulic line 132 a and the first manifold valve 122 a. The second hydraulic circuit 120 b includes a second longitudinal hydraulic line 132 b that extends between and fluidly connects the compression chamber port 130 b (to the second compression chamber 126 b) of the front right damper 102 b and the compression chamber port 130 b (to the fourth compression chamber 126 d) of the back right damper 102 d. The second hydraulic circuit 120 b includes a front hydraulic line 134 b that extends between and fluidly connects the second longitudinal hydraulic line 132 b and the rebound chamber port 130 a (to the first rebound chamber 128 a) of the front left damper 102 a. The second hydraulic circuit 120 b also includes a rear hydraulic line 136 b that extends between and fluidly connects the second longitudinal hydraulic line 132 b and the rebound chamber port 130 a (to the third rebound chamber 128 c) of the back left damper 102 c. The second hydraulic circuit 120 b further includes a second manifold hydraulic line 138 b that extends between and fluidly connects the second longitudinal hydraulic line 132 b and the second manifold valve 122 b. It should be appreciated that the word “longitudinal” as used in the first and second longitudinal hydraulic lines 132 a, 132 b simply means that the first and second longitudinal hydraulic lines 132 a, 132 b run between the front dampers 102 a, 102 b and the back dampers 102 c, 102 d generally. The first and second longitudinal hydraulic lines 132 a, 132 b need not be linear or arranged in any particular direction as long as they ultimately connect the front dampers 102 a, 102 b and the back dampers 102 c, 102 d.

The suspension system 100 also includes four bridge hydraulic lines 140 a, 140 b, 140 c, 140 d that fluidly couple the first and second hydraulic circuits 120 a, 120 b and each corner of the vehicle. The four bridge hydraulic lines 140 a, 140 b, 140 c, 140 d include a front left bridge hydraulic line 140 a that extends between and fluidly connects the first longitudinal hydraulic line 132 a of the first hydraulic circuit 120 a and the front hydraulic line 134 b of the second hydraulic circuit 120 b, a front right bridge hydraulic line 140 b that extends between and fluidly connects the front hydraulic line 134 a of the first hydraulic circuit 120 a and the second longitudinal hydraulic line 132 b of the second hydraulic circuit 120 b, a back left bridge hydraulic line 140 c that extends between and fluidly connects the first longitudinal hydraulic line 132 a of the first hydraulic circuit 120 a and the rear hydraulic line 136 b of the second hydraulic circuit 120 b, and a back right bridge hydraulic line 140 d that extends between and fluidly connects the rear hydraulic line 136 a of the first hydraulic circuit 120 a and the second longitudinal hydraulic line 132 b of the second hydraulic circuit 120 b.

The front left bridge hydraulic line 140 a is connected to the first longitudinal hydraulic line 132 a between the compression chamber port 130 b of the front left damper 102 a and the front hydraulic line 134 a of the first hydraulic circuit 120 a. The front right bridge hydraulic line 140 b is connected to the second longitudinal hydraulic line 132 b between the compression chamber port 130 b of the front right damper 102 b and the front hydraulic line 134 b of the second hydraulic circuit 120 b. The back left bridge hydraulic line 140 c is connected to the first longitudinal hydraulic line 132 a between the compression chamber port 130 b of the back left damper 102 c and the rear hydraulic line 136 a of the first hydraulic circuit 120 a. The back right bridge hydraulic line 140 d is connected to the second longitudinal hydraulic line 132 b between the compression chamber port 130 b of the back right damper 102 d and the rear hydraulic line 136 b of the second hydraulic circuit 120 b. In the illustrated example, the various hydraulic lines are made of flexible tubing (e.g., hydraulic hoses), but it should be appreciated that other conduit structures and/or fluid passageways can be used.

A front left accumulator 142 a is arranged in fluid communication with the first longitudinal hydraulic line 132 a at a location between the compression chamber port 130 b of the front left damper 102 a and the front left bridge hydraulic line 140 a. A front right accumulator 142 b is arranged in fluid communication with the second longitudinal hydraulic line 132 b at a location between the compression chamber port 130 b of the front right damper 102 b and the front right bridge hydraulic line 140 b. A back left accumulator 142 c is arranged in fluid communication with the first longitudinal hydraulic line 132 a at a location between the compression chamber port 130 b of the back left damper 102 c and the back left bridge hydraulic line 140 c. A back right accumulator 142 d is arranged in fluid communication with the second longitudinal hydraulic line 132 b at a location between the compression chamber port 130 b of the back right damper 102 d and the back right bridge hydraulic line 140 d. Each of the accumulators 142 a, 142 b, 142 c, 142 d have a variable fluid volume that increases and decreases depending on the fluid pressure in the first and second longitudinal hydraulic lines 132 a, 132 b. It should be appreciated that the accumulators 142 a, 142 b, 142 c, 142 d may be constructed in a number of different ways. For example and without limitation, the accumulators 142 a, 142 b, 142 c, 142 d may have accumulation chambers and pressurized gas chambers that are separated by floating pistons or flexible membranes.

The suspension system 100 also includes six electro-mechanical comfort valves 144 a, 144 b, 144 c, 144 d, 146 a, 146 b that are connected in-line (i.e., in series) with each of the bridge hydraulic lines 140 a, 140 b, 140 c, 140 d and each of the longitudinal hydraulic lines 132 a, 132 b. A front left comfort valve 144 a is positioned in the front left bridge hydraulic line 140 a. A front right comfort valve 144 b is positioned in the front right bridge hydraulic line 140 b. A back left comfort valve 144 c is positioned in the back left bridge hydraulic line 140 c. A back right comfort valve 144 d is positioned in the back right bridge hydraulic line 140 d. A first longitudinal comfort valve 146 a is positioned in the first longitudinal hydraulic line 132 a between the front and rear hydraulic lines 134 a, 136 a of the first hydraulic circuit 120 a. A second longitudinal comfort valve 146 b is positioned in the second longitudinal hydraulic line 132 b between the front and rear hydraulic lines 134 b, 136 b of the second hydraulic circuit 120 b. In the illustrated example, the comfort valves 144 a, 144 b, 144 c, 144 d and the longitudinal comfort valves 146 a, 146 b are semi-active electro-mechanical valves with a combination of passive spring-disk elements and a solenoid. The comfort valves 144 a, 144 b, 144 c, 144 d and the longitudinal comfort valves 146 a, 146 b are electronically connected to the controller, which is configured to supply electrical current to the solenoids of the comfort valves 144 a, 144 b, 144 c, 144 d and the longitudinal comfort valves 146 a, 146 b to selectively and individually open and close the comfort valves 144 a, 144 b, 144 c, 144 d and the longitudinal comfort valves 146 a, 146 b.

The first pressure sensor 124 a of the manifold assembly 104 is arranged to measure fluid pressure in the first manifold hydraulic line 138 a and the second pressure sensor 124 b of the manifold assembly 104 is arranged to measure fluid pressure in the second manifold hydraulic line 138 b. When the vehicle is cornering, braking, or accelerating, the lateral and longitudinal acceleration is measured by one or more accelerometers (not shown) and the anti-roll torque to control the roll of the vehicle is calculated by the controller. Alternatively, the lateral and longitudinal acceleration of the vehicle can be computed by the controller based on a variety of different inputs, including without limitation, steering angle, vehicle speed, brake pedal position, and/or accelerator pedal position. The dampers 102 a, 102 b, 102 c, 102 d are used to provide forces that counteract the roll moment induced by the lateral acceleration, thus reducing the roll angle of the vehicle.

When the first and second manifold valves 122 a, 122 b are closed, the first and second hydraulic circuits 120 a, 120 b operate as a closed loop system, either together or separately depending on the open or closed status of the electro-mechanical comfort valves 144 a, 144 b, 144 c, 144 d and the longitudinal comfort valves 146 a, 146 b. When the first and/or second manifold valves 122 a, 122 b are open, the bi-directional pump 110 either adds or removes fluid from the first and/or second hydraulic circuits 120 a, 120 b. As will be explained in greater detail below, the suspension system 100 can control the roll stiffness of the vehicle, which changes the degree to which the vehicle will lean to one side or the other during corning (i.e., roll)

For example, when the vehicle is put into a right-hand turn, the momentum of the sprung weight of the vehicle tends to make the vehicle lean left towards the outside of the turn, compressing the front left damper 102 a and the back left damper 102 c. When this occurs, fluid flows out from the first compression chamber 126 a of the front left damper 102 a and the third compression chamber 126 c of the back left damper 102 c into the first longitudinal hydraulic line 132 a of the first hydraulic circuit 120 a. As a result of the weight transfer to the left side of the vehicle, the front right damper 102 b and back right damper 102 d begin to extend, causing fluid to flow out of the second rebound chamber 128 b of the front right damper 102 b and the fourth compression chamber 126 d of the back right damper 102 d into the front and rear hydraulic lines 134 a, 136 a of the first hydraulic circuit 120 a. When the comfort valves 144 a, 144 b, 144 c, 144 d are closed, the fluid flow out of the first compression chamber 126 a of the front left damper 102 a, out of the third compression chamber 126 c of the back left damper 102 c, out of the second rebound chamber 128 b of the front right damper 102 b, and out of the fourth rebound chamber 128 d of the back right damper 102 d and into the front and rear hydraulic lines 134 a, 136 a of the first hydraulic circuit 120 a increases the pressure in the front left and back left accumulators 142 a, 142 c, thus providing a passive roll resistance where it becomes increasingly more difficult to compress the front left damper 102 a and the back left damper 102 c since the first compression chamber 126 a of the front left damper 102 a and the third compression chamber 126 c of the back left damper 102 c are connected in fluid communication with the first hydraulic circuit 120 a. At the same time, fluid flows out of front right and back right accumulators 142 b, 142 d and into the first rebound chamber 128 a of the front left damper 102 a, into the third rebound chamber 128 c of the back left damper 102 c, into the second compression chamber 126 b of the front right damper 102 b, and into the fourth compression chamber 126 d of the back right damper 102 d. The resulting pressure difference between the dampers 102 a, 102 b, 102 c, 102 d generates damper forces that counteract or resist the roll moment of the vehicle. Additional roll resistance can be added by opening the first manifold valve 122 a as the bi-directional pump 110 is running in a first direction where the bi-directional pump 110 draws in hydraulic fluid from the reservoir hydraulic line 118 and discharges hydraulic fluid into the pump hydraulic line 108 to produce a positive pressure in the pump hydraulic line 108, which increases fluid pressure in the first hydraulic circuit 120 a when the first manifold valve 122 a is open.

The opposite is true when the vehicle is put into a left-hand turn, where the momentum of the sprung weight of the vehicle tends to make the vehicle lean right towards the outside of the turn, compressing the front right damper 102 b and the back right damper 102 d. When this occurs, fluid flows out from the second compression chamber 126 b of the front right damper 102 b and the fourth compression chamber 126 d of the back right damper 102 d into the second longitudinal hydraulic line 132 b of the second hydraulic circuit 120 b. As a result of the weight transfer to the right side of the vehicle, the front left damper 102 a and back left damper 102 c begin to extend, causing fluid to flow out of the first rebound chamber 128 a of the front left damper 102 a and the third rebound chamber 128 c of the back left damper 102 c into the front and rear hydraulic lines 134 b, 136 b of the second hydraulic circuit 120 b. When the comfort valves 144 a, 144 b, 144 c, 144 d are closed, the fluid flow out of the second compression chamber 126 b of the front right damper 102 b, out of the fourth compression chamber 126 d of the back right damper 102 d, out of the first rebound chamber 128 a of the front left damper 102 a, and out of the third rebound chamber 128 c of the back left damper 102 c and into the front and rear hydraulic lines 134 b, 136 b of the second hydraulic circuit 120 b increases the pressure in the front right and back right accumulators 142 b, 142 d, thus providing a passive roll resistance where it becomes increasingly more difficult to compress the front right damper 102 b and the back right damper 102 d since the second compression chamber 126 b of the front right damper 102 b and the fourth compression chamber 126 d of the back right damper 102 d are connected in fluid communication with the second hydraulic circuit 120 b. At the same time, fluid flows out of front left and back left accumulators 142 a, 142 c and into the second rebound chamber 128 b of the front right damper 102 b, into the fourth rebound chamber 128 d of the back right damper 102 d, into the first compression chamber 126 a of the front left damper 102 a, and into the third compression chamber 126 c of the back left damper 102 c. The resulting pressure difference between the dampers 102 a, 102 b, 102 c, 102 d generates damper forces that counteract or resist the roll moment of the vehicle. Additional roll resistance can be added by opening the second manifold valve 122 b as the bi-directional pump 110 is running in the first direction where the bi-directional pump 110 draws in hydraulic fluid from the reservoir hydraulic line 118 and discharges hydraulic fluid into the pump hydraulic line 108 to produce a positive pressure in the pump hydraulic line 108, which increases fluid pressure in the second hydraulic circuit 120 b when the second manifold valve 122 b is open.

It should also be appreciated that during cornering, the roll stiffness of the front dampers 102 a, 102 b can be coupled or de-coupled from the roll stiffness of the rear dampers 102 c, 102 d by opening and closing the first and/or second longitudinal comfort valves 146 a, 146 b. For example, the roll stiffness of the front left damper 102 a and the back left damper 102 c will be coupled when the first longitudinal comfort valve 146 a is open and decoupled when the first longitudinal comfort valve 146 a is closed. Similarly, the roll stiffness of the front right damper 102 b and the back right damper 102 d will be coupled when the second longitudinal comfort valve 146 b is open and decoupled when the second longitudinal comfort valve 146 b is closed.

When roll stiffness is not required, the comfort valves 144 a, 144 b, 144 c, 144 d and the longitudinal comfort valves 146 a, 146 b can be opened to enhance the ride comfort of the suspension system 100 and reduce or eliminate unwanted suspension movements resulting from the hydraulic coupling of one damper of the system to another damper of the system (e.g., where the compression of one damper causes movement and/or a dampening change in another damper). For example, when the front left comfort valve 144 a is open and the front left damper 102 a undergoes a compression stroke as the front left wheel hits a bump, fluid may flow from the first compression chamber 126 a of the front left damper 102 a, into the first longitudinal hydraulic line 132 a, from the first longitudinal hydraulic line 132 a to the front hydraulic line 134 b of the second hydraulic circuit 120 b by passing through the front left bridge hydraulic line 140 a and the front left comfort valve 144 a, and into the first rebound chamber 128 a of the front left damper 102 a. Thus, fluid can travel from the first compression chamber 126 a to the first rebound chamber 128 a of the front left damper 102 a with the only restriction coming from the dampening valves in the rebound and compression chamber ports 130 a, 130 b of the front left damper 102 a. As such, when all of the comfort valves 144 a, 144 b, 144 c, 144 d and the longitudinal comfort valves 146 a, 146 b are open, the dampers 102 a, 102 b, 102 c, 102 d are effectively decoupled from one another for improved ride comfort. It should also be appreciated that to return the suspension system 100 to this “comfort mode” of operation, the first and/or second manifold valves 122 a, 122 b may be opened while the bi-directional pump 110 is running in a second direction where the bi-directional pump 110 draws in hydraulic fluid from the pump hydraulic line 108 and discharges hydraulic fluid into the reservoir hydraulic line 118 to produce a negative pressure in the pump hydraulic line 108 that reduces fluid pressure in the first and/or second hydraulic circuits 120 a, 120 b.

FIG. 2 illustrates another suspension system 200 that shares many of the same components as the suspension system 100 illustrated in FIG. 1 , but in FIG. 2 a front axle lift assembly 248 has been added. Rather than repeat the description set forth above, the following paragraphs describe the structure and function of the components in FIG. 2 that are new and/or different from those shown and described in connection with FIG. 1 . It should be appreciated that the reference numbers in FIG. 1 are “100” series numbers (e.g., 100, 102, 104, etc.) whereas the components in FIG. 2 that are the same or similar to the components of the suspension system 100 shown in FIG. 1 share the same base reference numbers, but are listed as “200” series numbers (e.g., 200, 202, 204, etc.). Thus, the same description for element 100 above applies to element 200 in FIG. 2 and so on and so forth.

The front axle lift assembly 248 illustrated in FIG. 2 includes a front left lifter 250 a on the front left damper 202 a and a front right lifter 250 b on the front right damper 202 b. Although other configurations are possible, in the illustrated example, the front left damper 202 a and the front right damper 202 b include a front left coil spring 252 a and a front right coil spring 252 b, respectively, that extend co-axially and helically about the piston rods of the front dampers 202 a, 202 b in a coil-over arrangement. The front lifters 250 a, 250 b are positioned between the front coils springs 252 a, 252 b and the first and second rebound chambers 228 a, 228 b of the front dampers 202 a, 202 b and extend co-axially and annularly about the piston rods. The manifold assembly 204 further includes a third manifold valve 222 c that is connected in fluid communication with the pump hydraulic line 208. A front axle lift hydraulic line 254 a extends between and is fluidly connected to the third manifold valve 222 c with the front left lifter 250 a and the front right lifter 250 b. A third pressure sensor 224 c is arranged to monitor the fluid pressure in the front axle lift hydraulic line 254 a. Each front lifter 250 a, 250 b is axially expandable such that an increase in fluid pressure inside the front lifters 250 a, 250 b causes the front lifters 250 a, 250 b to urge the front coil springs 252 a, 252 b away from the first and second rebound chambers 228 a, 228 b of the front dampers 202 a, 202 b, which operates to lift (i.e., raise) the front of the vehicle, increasing the ride height. To activate the front axle lift assembly 248, the controller opens the third manifold valve 222 c when the bi-directional pump 210 is running in the first direction where the bi-directional pump 210 draws in hydraulic fluid from the reservoir hydraulic line 218 and discharges hydraulic fluid into the pump hydraulic line 208 to produce a positive pressure in the pump hydraulic line 208, which increases fluid pressure in the front axle lift hydraulic line 254 a and thus the front lifters 250 a, 250 b. Once a desired lift position is achieved, the controller closes the third manifold valve 222 c. It should therefore be appreciated that the front axle lift assembly 248 can be used to provide improved ground clearance during off-road operation or to give low riding vehicles improved ground clearance when traversing speed bumps. To deactivate the front axle lift assembly 248, the controller opens the third manifold valve 222 c when the bi-directional pump 210 is running in the second direction where the bi-directional pump 210 draws in hydraulic fluid from the pump hydraulic line 208 and discharges hydraulic fluid into the reservoir hydraulic line 218 to produce a negative pressure in the pump hydraulic line 208 that reduces fluid pressure in the front axle lift hydraulic line 254 a to lower the front of the vehicle back down to an unlifted position.

FIG. 3 illustrates another suspension system 300 that shares many of the same components as the suspension systems 100, 200 illustrated in FIGS. 1 and 2 , but in FIG. 3 a rear axle lift assembly 356 has been added. Rather than repeat the description set forth above, the following paragraphs describe the structure and function of the components in FIG. 3 that are new and/or different from those shown and described in connection with FIGS. 1 and 2 . It should be appreciated that the reference numbers in FIG. 1 are “100” series numbers (e.g., 100, 102, 104, etc.) and the reference numbers in FIG. 2 are “200” series numbers (e.g., 200, 202, 204, etc.) whereas the components in FIG. 3 that are the same or similar to the components of the suspension systems 100, 200 shown in FIGS. 1 and 2 share the same base reference numbers, but are listed as “300” series numbers (e.g., 300, 302, 304, etc.). Thus, the same description for elements 100 and 200 above applies to element 300 in FIG. 3 and so on and so forth.

The rear axle lift assembly 356 illustrated in FIG. 3 includes a back left lifter 350 c on the back left damper 302 c and a back right lifter 350 d on the back right damper 302 d. Although other configurations are possible, in the illustrated example, the back left damper 302 c and the back right damper 302 d include a back left coil spring 352 c and a back right coil spring 352 d, respectively, that extend co-axially and helically about the piston rods of the back dampers 302 c, 302 d in a coil-over arrangement. The back lifters 350 c, 350 d are positioned between the back coils springs 352 c, 352 d and the third and fourth rebound chambers 328 c, 328 d of the back dampers 302 a, 302 b and extend co-axially and annularly about the piston rods. The manifold assembly 304 further includes a fourth manifold valve 322 d that is connected in fluid communication with the pump hydraulic line 308. A rear axle lift hydraulic line 354 b extends between and is fluidly connected to the fourth manifold valve 322 d with the back left lifter 350 c and the back right lifter 350 d. A fourth pressure sensor 324 d is arranged to monitor the fluid pressure in the rear axle lift hydraulic line 354 b. Each back lifter 350 c, 350 d is axially expandable such that an increase in fluid pressure inside the back lifters 350 c, 350 d causes the back lifters 350 c, 350 d to urge the back coil springs 352 c, 352 d away from the third and fourth rebound chambers 328 c, 328 d of the back dampers 302 c, 302 d, which operates to lift (i.e., raise) the back/rear of the vehicle, increasing the ride height. To activate the rear axle lift assembly 356, the controller opens the fourth manifold valve 322 d when the bi-directional pump 310 is running in the first direction where the bi-directional pump 310 draws in hydraulic fluid from the reservoir hydraulic line 318 and discharges hydraulic fluid into the pump hydraulic line 308 to produce a positive pressure in the pump hydraulic line 308, which increases fluid pressure in the rear axle lift hydraulic line 354 b and thus the back lifters 350 c, 350 d. Once a desired lift position is achieved, the controller closes the fourth manifold valve 322 d. It should therefore be appreciated that the rear axle lift assembly 356 can be used in combination with the front axle lift assembly 348 (also described above in connection with FIG. 2 ) to provide improved ground clearance during off-road operation or to give low riding vehicles improved ground clearance when traversing speed bumps. To deactivate the rear axle lift assembly 356, the controller opens the fourth manifold valve 322D when the bi-directional pump 310 is running in the second direction where the bi-directional pump 310 draws in hydraulic fluid from the pump hydraulic line 308 and discharges hydraulic fluid into the reservoir hydraulic line 318 to produces a negative pressure in the pump hydraulic line 308 that reduces fluid pressure in the rear axle lift hydraulic line 354 b to lower the rear of the vehicle back down to an unlifted position.

With reference to FIG. 4 , another suspension system 400 is illustrated that shares many of the same components as the suspension system 100 illustrated in FIG. 1 . Rather than repeat the description set forth above, the following paragraphs describe the structure and function of the components in FIG. 4 that are new and/or different from those shown and described in connection with FIG. 1 . It should be appreciated that the reference numbers in FIG. 1 are “100” series numbers (e.g., 100, 102, 104, etc.) whereas the components in FIG. 4 that are the same or similar to the components of the suspension system 100 shown in FIG. 1 share the same base reference numbers, but are listed as “400” series numbers (e.g., 400, 402, 404, etc.). Thus, the same description for element 100 above applies to element 400 in FIG. 4 and so on and so forth.

The suspension system 400 in FIG. 4 also includes a front left damper 402 a, a front right damper 402 b, a back left damper 402 c, and a back right damper 402 d. The suspension system 400 also includes a manifold assembly 404 that is connected in fluid communication with a pump assembly 406 by a pump hydraulic line 408. Like in FIG. 1 , the pump assembly 406 includes a bi-directional pump 410, a hydraulic reservoir 412 (e.g., a tank), and a bypass hydraulic line 414 that can be open and closed by a pressure relief valve 416.

The manifold assembly 404 is connected in fluid communication with the front and rear dampers 402 a, 402 b, 402 c, 402 d by four hydraulic circuits 420 a, 420 b, 420 c, 420 d: a first hydraulic circuit 420 a, a second hydraulic circuit 420 b, a third hydraulic circuit 420 c, and a fourth hydraulic circuit 420 d. The manifold assembly 404 includes four manifold valves 422 a, 422 b, 422 c, 422 d (a first manifold valve 422 a, a second manifold valve 422 b, a third manifold valve 422 c, and a fourth manifold valve 422 d) that are connected in parallel with the pump hydraulic line 408. The manifold assembly 404 further includes a first manifold comfort valve 460 a, a second manifold comfort valve 460 b, and six manifold conduits 462 a, 462 b, 462 c, 462 d, 462 e, 462 f: a first manifold conduit 462 a, a second manifold conduit 462 b, a third manifold conduit 462 c, a fourth manifold conduit 462 d, a fifth manifold conduit 462 e, and a sixth manifold conduit 462 f. The first manifold conduit 462 a is connected in fluid communication with the first manifold valve 422 a and the first manifold comfort valve 460 a while the second manifold conduit 462 b is connected in fluid communication with the second manifold valve 422 b and the second manifold comfort valve 460 b. The third manifold conduit 462 c is connected in fluid communication with the third manifold valve 422 c and the fourth manifold conduit 462 d is connected in fluid communication with the fourth manifold valve 422 d. The fifth manifold conduit 462 e is connected in fluid communication with the first manifold comfort valve 460 a and the sixth manifold conduit 462 f is connected in fluid communication with the second manifold comfort valve 460 b. Additional structure and operational details of the manifold assembly 404 is described below in connection with FIG. 5 ; however, it should be appreciated from FIG. 4 that fluid pressure in the four hydraulic circuits 420 a, 420 b, 420 c, 420 d operates to dynamically adjust the roll and pitch stiffness of the vehicle and can be used to either augment or completely replace mechanical stabilizer bars/anti-roll bars. Such mechanical systems require relatively straight, unobstructed runs between each of the front dampers 402 a, 402 b and each of the back dampers 402 c, 402 d. Accordingly, the suspension system 400 disclosed herein offers packaging benefits because the dampers 402 a, 402 b, 402 c, 402 d only need to be hydraulically connected to the manifold assembly 404.

The first hydraulic circuit 420 a includes a first cross-over hydraulic line 464 a that extends between and fluidly connects the compression chamber port 430 b (to the first compression chamber 426 a) of the front left damper 402 a and the rebound chamber port 430 a (to the fourth rebound chamber 428 d) of the back right damper 402 d. The first hydraulic circuit 420 a also includes a first manifold hydraulic line 438 a that extends between and fluidly connects the first cross-over hydraulic line 464 a and the first manifold conduit 462 a. The second hydraulic circuit 420 b includes a second cross-over hydraulic line 464 b that extends between and fluidly connects the compression chamber port 430 b (to the second compression chamber 426 b) of the front right damper 402 b and the rebound chamber port 430 a (to the third rebound chamber 428 c) of the back left damper 402 c. The second hydraulic circuit 420 b also includes a second manifold hydraulic line 438 b that extends between and fluidly connects the second cross-over hydraulic line 464 b and the second manifold conduit 462 b. The third hydraulic circuit 420 c includes a third cross-over hydraulic line 464 c that extends between and fluidly connects the rebound chamber port 430 a (to the first rebound chamber 428 a) of the front left damper 402 a and the compression chamber port 430 b (to the fourth compression chamber 426 d) of the back right damper 402 d. The third hydraulic circuit 420 c also includes a third manifold hydraulic line 438 c that extends between and fluidly connects the third cross-over hydraulic line 464 c and the sixth manifold conduit 462 f. The fourth hydraulic circuit 420 d includes a fourth cross-over hydraulic line 464 d that extends between and fluidly connects the rebound chamber port 430 a (to the second rebound chamber 428 b) of the front right damper 402 b and the compression chamber port 430 b (to the third compression chamber 426 c) of the back left damper 402 c. The fourth hydraulic circuit 420 d also includes a fourth manifold hydraulic line 438 d that extends between and fluidly connects the fourth cross-over hydraulic line 464 d and the fifth manifold conduit 462 e. It should be appreciated that the word “cross-over” as used in the first, second, third, and fourth cross-over hydraulic lines 464 a, 464 b, 464 c, 464 d simply means that the first, second, third, and fourth cross-over hydraulic lines 464 a, 464 b, 464 c, 464 d run between dampers 402 a, 402 b, 402 c, 402 d at opposite corners of the vehicle (e.g., front left to back right and front right to back left). The first, second, third, and fourth cross-over hydraulic lines 464 a, 464 b, 464 c, 464 d need not be linear or arranged in any particular direction as long as they ultimately connect dampers 402 a, 402 b, 402 c, 402 d positioned at opposite corners of the vehicle.

The suspension system 400 also includes four bridge hydraulic lines 440 a, 440 b, 440 c, 440 d that fluidly couple the first and third hydraulic circuits 420 a, 420 c and the second and fourth hydraulic circuits 420 b, 420 d to one another. The four bridge hydraulic lines 440 a, 440 b, 440 c, 440 d include a front left bridge hydraulic line 440 a that extends between and fluidly connects the first cross-over hydraulic line 464 a and the third cross-over hydraulic line 464 c, a front right bridge hydraulic line 440 b that extends between and fluidly connects the second cross-over hydraulic line 464 b and the fourth cross-over hydraulic line 464 d, a back left bridge hydraulic line 440 c that extends between and fluidly connects the second cross-over hydraulic line 464 b and the fourth cross-over hydraulic line 464 d, and a back right bridge hydraulic line 440 d that extends between and fluidly connects the first cross-over hydraulic line 464 a and the third cross-over hydraulic line 464 c.

The front left bridge hydraulic line 440 a is connected to the first cross-over hydraulic line 464 a between the compression chamber port 430 b of the front left damper 402 a and the first manifold hydraulic line 438 a and is connected to the third cross-over hydraulic line 464 c between the rebound chamber port 430 a of the front left damper 402 a and the third manifold hydraulic line 438 c. The front right bridge hydraulic line 440 b is connected to the second cross-over hydraulic line 464 b between the compression chamber port 430 b of the front right damper 402 b and the second manifold hydraulic line 438 b and is connected to the fourth cross-over hydraulic line 464 d between the rebound chamber port 430 a of the front right damper 402 b and the fourth manifold hydraulic line 438 d. The back left bridge hydraulic line 440 c is connected to the second cross-over hydraulic line 464 b between the rebound chamber port 430 a of the back left damper 402 c and the second manifold hydraulic line 438 b and is connected to the fourth cross-over hydraulic line 464 d between the compression chamber port 430 b of the back left damper 402 c and the fourth manifold hydraulic line 438 d. The back right bridge hydraulic line 440 d is connected to the first cross-over hydraulic line 464 a between the rebound chamber port 430 a of the back right damper 402 d and the first manifold hydraulic line 438 a and is connected to the third cross-over hydraulic line 464 c between the compression chamber port 430 b of the back right damper 402 d and the third manifold hydraulic line 438 c. In the illustrated example, the various hydraulic lines are made of flexible tubing (e.g., hydraulic hoses), but it should be appreciated that other conduit structures and/or fluid passageways can be used.

A front left accumulator 442 a is arranged in fluid communication with the first cross-over hydraulic line 464 a at a location between the compression chamber port 430 b of the front left damper 402 a and the front left bridge hydraulic line 440 a. A front right accumulator 442 b is arranged in fluid communication with the second cross-over hydraulic line 464 b at a location between the compression chamber port 430 b of the front right damper 402 b and the front right bridge hydraulic line 440 b. A back left accumulator 442 c is arranged in fluid communication with the fourth cross-over hydraulic line 464 d at a location between the compression chamber port 430 b of the back left damper 402 c and the back left bridge hydraulic circuit 420 c. A back right accumulator 442 d is arranged in fluid communication with the third cross-over hydraulic line 464 c at a location between the compression chamber port 430 b of the back right damper 402 d and the back right bridge hydraulic line 440 d. Each of the accumulators 442 a, 442 b, 442 c, 442 d have a variable fluid volume that increases and decreases depending on the fluid pressure in the first and second longitudinal hydraulic lines 432 a, 432 b. It should be appreciated that the accumulators 442 a, 442 b, 442 c, 442 d may be constructed in a number of different ways. For example and without limitation, the accumulators 442 a, 442 b, 442 c, 442 d may have accumulation chambers and pressurized gas chambers that are separated by floating pistons or flexible membranes.

The suspension system 400 also includes four electro-mechanical comfort valves 444 a, 444 b, 444 c, 444 d that are connected in-line (i.e., in series) with each of the bridge hydraulic lines 440 a, 440 b, 440 c, 440 d. A front left comfort valve 444 a is positioned in the front left bridge hydraulic line 440 a. A front right comfort valve 444 b is positioned in the front right bridge hydraulic line 440 b. A back left comfort valve 444 c is positioned in the back left bridge hydraulic line 440 c. A back right comfort valve 444 d is positioned in the back right bridge hydraulic line 440 d. In the illustrated example, the four comfort valves 444 a, 444 b, 444 c, 444 d and the two manifold comfort valves 460 a, 460 b are semi-active electro-mechanical valves with a combination of passive spring-disk elements and a solenoid. The comfort valves 444 a, 444 b, 444 c, 444 d and the two manifold comfort valves 460 a, 460 b are electronically connected to the controller, which is configured to supply electrical current to the solenoids of the comfort valves 444 a, 444 b, 444 c, 444 d and the two manifold comfort valves 460 a, 460 b to selectively and individually open and close the comfort valves 444 a, 444 b, 444 c, 444 d and the two manifold comfort valves 460 a, 460 b.

When the manifold valves 422 a, 422 b, 422 c, 422 d are closed, the hydraulic circuits 420 a, 420 b, 420 c, 420 d operate as a closed loop system, either together or separately depending on the open or closed status of the comfort valves 444 a, 444 b, 444 c, 444 d and manifold comfort valves 460 a, 460 b. When the manifold valves 422 a, 422 b, 422 c, 422 d are open, the bi-directional pump 110 either adds or removes fluid from one or more of the hydraulic circuits 420 a, 420 b, 420 c, 420 d. There are three primary types of suspension movements that the illustrated suspension system 400 can control either passively (i.e., as a closed loop system) or actively (i.e., as an open loop system) by changing or adapting the roll and/or pitch stiffness of the vehicle: leaning to one side or the other during cornering (i.e., roll) pitching forward during braking (i.e., brake dive), and pitching aft during acceleration (i.e., rear end squat). Descriptions of how the suspension system 400 reacts to each of these conditions are provided below.

When the vehicle is put into a right-hand turn, the momentum of the sprung weight of the vehicle tends to make the vehicle lean left towards the outside of the turn, compressing the front left damper 402 a and the back left damper 402 c. When this occurs, fluid flows out from the first compression chamber 426 a of the front left damper 402 a and the third compression chamber 426 c of the back left damper 402 c into the first and fourth cross-over hydraulic lines 464 a, 464 d. As a result of the weight transfer to the left side of the vehicle, the front right damper 402 b and back right damper 402 d begin to extend, causing fluid to flow out of the second rebound chamber 428 b of the front right damper 402 b and the fourth rebound chamber 428 d of the back right damper 402 d into the first and fourth cross-over hydraulic lines 464 a, 464 d. When the comfort valves 444 a, 444 b, 444 c, 444 d are closed, the fluid flow out of the first compression chamber 426 a of the front left damper 402 a, out of the third compression chamber 426 c of the back left damper 402 c, out of the second rebound chamber 428 b of the front right damper 402 b, and out of the fourth rebound chamber 428 d of the back right damper 402 d and into the first and fourth cross-over hydraulic lines 464 a, 464 d increases the pressure in the front left and back left accumulators 442 a, 442 c, thus providing a passive roll resistance where it becomes increasingly more difficult to compress the front left damper 402 a and the back left damper 402 c since the first compression chamber 426 a of the front left damper 402 a and the third compression chamber 426 c of the back left damper 402 c are connected in fluid communication with the first and fourth hydraulic circuits 420 a, 420 d. At the same time, fluid flows out of front right and back right accumulators 442 b, 442 d and into the first rebound chamber 428 a of the front left damper 402 a, into the third rebound chamber 428 c of the back left damper 402 c, into the second compression chamber 426 b of the front right damper 402 b, and into the fourth compression chamber 426 d of the back right damper 402 d. The resulting pressure difference between the dampers 402 a, 402 b, 402 c, 402 d generates damper forces that counteract or resist the roll moment of the vehicle. Additional roll resistance can be added by opening the first manifold valve 422 a and the first manifold comfort valve 460 a as the bi-directional pump 410 is running in a first direction where the bi-directional pump 410 draws in hydraulic fluid from the reservoir hydraulic line 418 and discharges hydraulic fluid into the pump hydraulic line 408 to produce a positive pressure in the pump hydraulic line 408, which increases fluid pressure in the first and fourth hydraulic circuits 420 a, 420 d.

The opposite is true when the vehicle is put into a left-hand turn, where the momentum of the sprung weight of the vehicle tends to make the vehicle lean right towards the outside of the turn, compressing the front right damper 402 b and the back right damper 402 d. When this occurs, fluid flows out from the second compression chamber 426 b of the front right damper 402 b and the fourth compression chamber 426 d of the back right damper 402 d into the second and third cross-over hydraulic lines 464 b, 464 c. As a result of the weight transfer to the right side of the vehicle, the front left damper 402 a and back left damper 402 c begin to extend, causing fluid to flow out of the first rebound chamber 428 a of the front left damper 402 a and the third rebound chamber 428 c of the back left damper 402 c into the second and third cross-over hydraulic lines 464 b, 464 c. When the comfort valves 444 a, 444 b, 444 c, 444 d are closed, the fluid flow out of the second compression chamber 426 b of the front right damper 402 b, out of the fourth compression chamber 426 d of the back right damper 402 d, out of the first rebound chamber 428 a of the front left damper 402 a, and out of the third rebound chamber 428 c of the back left damper 402 c and into the second and third cross-over hydraulic lines 464 b, 464 c increases the pressure in the front right and back right accumulators 142 b, 142 d, thus providing a passive roll resistance where it becomes increasingly more difficult to compress the front right damper 402 b and the back right damper 402 d since the second compression chamber 426 b of the front right damper 402 b and the fourth compression chamber 426 d of the back right damper 402 d are connected in fluid communication with the second and third hydraulic circuits 420 b, 420 c. At the same time, fluid flows out of front left and back left accumulators 442 a, 442 c and into the second rebound chamber 428 b of the front right damper 402 b, into the fourth rebound chamber 428 d of the back right damper 402 d, into the first compression chamber 426 a of the front left damper 402 a, and into the third compression chamber 426 c of the back left damper 402 c. The resulting pressure difference between the dampers 402 a, 402 b, 402 c, 402 d generates damper forces that counteract or resist the roll moment of the vehicle. Additional roll resistance can be added by opening the second manifold valve 422 b and the second manifold comfort valve 460 b as the bi-directional pump 410 is running in the first direction where the bi-directional pump 410 draws in hydraulic fluid from the reservoir hydraulic line 418 and discharges hydraulic fluid into the pump hydraulic line 408 to produce a positive pressure in the pump hydraulic line 408, which increases fluid pressure in the second and third hydraulic circuits 420 b, 420 c.

During braking, the momentum of the sprung weight of the vehicle tends to make the vehicle pitch or dive forward, compressing the front left damper 402 a and the front right damper 402 b. When this occurs, fluid flows out from the first compression chamber 426 a of the front left damper 402 a into the first cross-over hydraulic line 464 a and out from the second compression chamber 426 b of the front right damper 402 b into the second cross-over hydraulic line 464 b. As a result of the weight transfer to the front of the vehicle, the back left damper 402 c and back right damper 402 d begin to extend, causing fluid to flow out of the third rebound chamber 428 c of the back left damper 402 c into the second cross-over hydraulic line 464 b and out of the fourth rebound chamber 428 d of the back right damper 402 d into the first cross-over hydraulic line 464 a. With the front left, front right, back left, and back right comfort valves 444 a, 444 b, 444 c, 444 d and the first and second manifold comfort valves 460 a, 460 b all closed, the fluid flow out of the third rebound chamber 428 c of the back left damper 402 c and the fourth rebound chamber 428 d of the back right damper 402 d into the first and second cross-over hydraulic lines 464 a, 464 b increases the pressure in the front left and front right accumulators 442 a, 442 b, thus providing a passive pitch resistance where it becomes increasingly more difficult to compress the front left damper 402 a and the front right damper 402 b since the first compression chamber 426 a of the front left damper 402 a and the second compression chamber 426 b of the front right damper 402 b are connected in fluid communication with the first and second hydraulic circuits 420 a, 420 b.

During acceleration, the momentum of the sprung weight of the vehicle tends to make the vehicle pitch or squat rearward (i.e., aft), compressing the back left damper 402 c and the back right damper 402 d. When this occurs, fluid flows out from the third compression chamber 426 c of the back left damper 402 c into the fourth cross-over hydraulic line 464 d and out of the fourth compression chamber 426 d of the back right damper 402 d into the third cross-over hydraulic line 464 c. As a result of the weight transfer to the back/rear of the vehicle, the front left damper 402 a and front right damper 402 b begin to extend, causing fluid to flow out of the first rebound chamber 428 a of the front left damper 402 a into the third cross-over hydraulic line 464 c and out of the second rebound chamber 428 b of the front right damper 402 b into the fourth cross-over hydraulic line 464 d. With the front left, front right, back left, and back right comfort valves 444 a, 444 b, 444 c, 444 d and the first and second manifold comfort valves 460 a, 460 b all closed, the fluid flow out of the first rebound chamber 428 a of the front left damper 402 a and the second rebound chamber 428 b of the front right damper 402 b into the third and fourth cross-over hydraulic lines 464 c, 464 d increases the pressure in the back left and back right accumulators 442 c, 442 d, thus providing a passive pitch resistance where it becomes increasingly more difficult to compress the back left damper 402 c and the back right damper 402 d since the third compression chamber 426 c of the back left damper 402 c and the fourth compression chamber 426 d of the back right damper 402 d are connected in fluid communication with the third and fourth hydraulic circuits 420 c, 420 d.

When active or passive roll and/or pitch stiffness is not required, the four comfort valves 444 a, 444 b, 444 c, 444 d and the two manifold comfort valves 460 a, 460 b can be opened to enhance the ride comfort of the suspension system 400 and reduce or eliminate unwanted suspension movements resulting from the hydraulic coupling of one damper of the system to another damper of the system (e.g., where the compression of one damper causes movement and/or a dampening change in another damper). For example, when the front left comfort valve 444 a is open and the front left damper 402 a undergoes a compression stroke as the front wheel hits a bump, fluid may flow from the first compression chamber 426 a of the front left damper 402 a, into the first cross-over hydraulic line 464 a, from the first cross-over hydraulic line 464 a to the third cross-over hydraulic line 464 c by passing through the front left bridge hydraulic line 440 a and the front left comfort valve 444 a, and into the first rebound chamber 428 a of the front left damper 402 a. Thus, fluid can travel from the first compression chamber 426 a to the first rebound chamber 428 a of the front left damper 402 a with the only restriction coming from the dampening valves in the rebound and compression chamber ports 430 a, 430 b of the front left damper 402 a. As such, when all of the comfort valves 444 a, 444 b, 444 c, 444 d and the manifold comfort valves 460 a, 460 b are open, the dampers 402 a, 402 b, 402 c, 402 d are effectively decoupled from one another for improved ride comfort. It should also be appreciated that to return the suspension system 400 to this “comfort mode” of operation, the manifold valves 422 a, 422 b, 422 c, 422 d and/or the manifold comfort valves 460 a, 460 b may be opened while the bi-directional pump 410 is running in a second direction where the bi-directional pump 410 draws in hydraulic fluid from the pump hydraulic line 408 and discharges hydraulic fluid into the reservoir hydraulic line 418 to produce a negative pressure in the pump hydraulic line 408 that reduces fluid pressure in the hydraulic circuits 420 a, 420 b, 420 c, 420 d of the suspension system 400.

FIG. 5 illustrates the manifold assembly 404 of the suspension system 400 in more detail. The manifold assembly 404 includes first and second piston bores 466 a, 466 b that slidingly receive first and second floating pistons 468 a, 468 b, respectively. Each floating piston 468 a, 468 b includes a piston rod 458 and first and second piston heads 470 a, 470 b that are fixably coupled to opposing ends of the piston rod 458. A chamber divider 472 is fixably mounted at a midpoint of each of the first and second piston bores 466 a, 466 b. Each chamber divider 472 includes a through-bore that slidingly receives the piston rod 458. As such, the first piston bore 466 a is divided by the first floating piston 468 a into a first piston chamber 474 a that is arranged in fluid communication with the first manifold conduit 462 a, a second piston chamber 474 b disposed between the first piston head 470 a of the first floating piston 468 a and the chamber divider 472 in the first piston bore 466 a, a third piston chamber 474 c disposed between the second piston head 470 b of the first floating piston 468 a and the chamber divider 472 in the first piston bore 466 a, and a fourth piston chamber 474 d that is arranged in fluid communication with the fifth manifold conduit 462 e. Similarly, the second piston bore 466 b is divided by the second floating piston 468 b into a fifth piston chamber 474 e that is arranged in fluid communication with the second manifold conduit 462 b, a sixth piston chamber 474 f disposed between the first piston head 470 a of the second floating piston 468 b and the chamber divider 472 in the second piston bore 466 b, a seventh piston chamber 474 g disposed between the second piston head 470 b of the second floating piston 468 b and the chamber divider 472 in the second piston bore 466 b, and an eighth piston chamber 474 h that is arranged in fluid communication with the sixth manifold conduit 462 f. Optionally, biasing members (e.g., springs) (not shown) may be placed in the second, third, sixth, and seventh piston chambers 474 b, 474 c, 474 f, 474 g to naturally bias the first and second floating pistons 468 a, 468 b to a centered position where the second and third piston chambers 474 b, 474 c and the sixth and seventh piston chambers 474 f, 474 g have equal volumes.

The first manifold conduit 462 a is arranged in fluid communication with the first manifold hydraulic line 438 a, the second manifold conduit 462 b is arranged in fluid communication with the second manifold hydraulic line 438 b, the fifth manifold conduit 462 e is arranged in fluid communication with the fourth manifold hydraulic line 438 d, and the sixth manifold conduit 462 f is arranged in fluid communication with the third manifold hydraulic line 438 c. The third manifold conduit 462 c is arranged in fluid communication with the second and sixth piston chambers 474 b, 474 f while the fourth manifold conduit 462 d is arranged in fluid communication with the third and seventh piston chambers 474 c, 474 g. As a result, fluid pressure in the fourth piston chamber 474 d and thus the fifth manifold conduit 462 e can be increased independently of the first manifold conduit 462 a by closing the first manifold comfort valve 460 a and opening the fourth manifold valve 422 d when the bi-directional pump 410 is running in the first direction, which increases pressure in the third piston chamber 474 c and urges the first floating piston 468 a to the right in FIG. 5 , decreasing the volume of the fourth piston chamber 474 d and increasing the pressure in the fourth piston chamber 474 d. Similarly, fluid pressure in the eighth piston chamber 474 h and thus the sixth manifold conduit 462 f can be increased independently of the second manifold conduit 462 b by closing the second manifold comfort valve 460 b and opening the fourth manifold valve 422 d when the bi-directional pump 410 is running in the first direction, which increases pressure in the seventh piston chamber 474 g and urges the second floating piston 468 b to the right in FIG. 5 , decreasing the volume of the eighth piston chamber 474 h and increasing the pressure in the eighth piston chamber 474 h.

Fluid pressure in the first piston chamber 474 a and thus the first manifold conduit 462 a can also be increased without opening the first manifold valve 422 a by actuating the first floating piston 468 a, where the first manifold comfort valve 460 a is closed and the third manifold valve 422 c is open when the bi-directional pump 410 is running in the first direction, which increases pressure in the second piston chamber 474 b and urges the first floating piston 468 a to the left in FIG. 5 , decreasing the volume of the first piston chamber 474 a and increasing the pressure in the first piston chamber 474 a. Similarly, fluid pressure in the fifth piston chamber 474 e and the second manifold conduit 462 b can also be increased without opening the second manifold valve 422 b by actuating the second floating piston 468 b, where the second manifold comfort valve 460 b is closed and the third manifold valve 422 c is open when the bi-directional pump 410 is running in the first direction, which increases pressure in the sixth piston chamber 474 f and urges the second floating piston 468 b to the left in FIG. 5 , decreasing the volume of the fifth piston chamber 474 e and increasing the pressure in the second piston chamber 474 e.

The manifold assembly 404 may further include a first manifold accumulator 476 a that is arranged in fluid communication with the third manifold conduit 462 c between the third manifold valve 422 c and the second and sixth piston chambers 474 b, 474 f and a second manifold accumulator 476 b that is arranged in fluid communication with the fourth manifold conduit 462 d between the third and seventh piston chambers 474 c, 474 g. The first and second manifold accumulators 476 a, 476 b may be constructed in a number of different ways. For example and without limitation, the first and second manifold accumulators 476 a, 476 b may have accumulation chambers and pressurized gas chambers that are separated by floating pistons or flexible membranes. Under braking, fluid flow within the four hydraulic circuits generates a pressure difference between the first and second manifold accumulators 476 a, 476 b, which in turn causes an increase in pressure in the front left and front right accumulators 442 a, 442 b and provides a pitch stiffness that resists the compression of the front dampers 402 a, 402 b and rebound/extension of the back dampers 402 c, 402 d. Under acceleration, fluid flow within the four hydraulic circuits generates an opposite pressure difference between the first and second manifold accumulators 476 a, 476 b, which in turn causes an increase in pressure in the back left and back right accumulators 442 c, 442 d and provides a pitch stiffness that resists the rebound/extension of the front dampers 402 a, 402 b and compression of the back dampers 402 c, 402 d. Additional pitch resistance can be added before a braking or acceleration event by opening the third and fourth manifold valves 422 c, 422 d as the bi-directional pump 410 is running in the first direction. The bi-directional pump 410 draws in hydraulic fluid from the reservoir hydraulic line 418 and discharges hydraulic fluid into the pump hydraulic line 408 to produce a positive pressure in the pump hydraulic line 408, which increases fluid pressure in the first and second manifold accumulators 476 a, 476 b. In a similar way, the pitch stiffness of the system can be reduced before a braking or acceleration event by running the bi-directional pump 410 in the second direction while opening the third and fourth manifold valves 422 c, 422 d.

The manifold assembly 404 may also include six pressure sensors 424 a, 424 b, 424 c, 424 d, 424 e, 424 f: a first pressure sensor 424 a arranged to monitor fluid pressure in the first manifold conduit 462 a, a second pressure sensor 424 b arranged to monitor fluid pressure in the second manifold conduit 462 b, a third pressure sensor 424 c arranged to monitor fluid pressure in the third manifold conduit 462 c, a fourth pressure sensor 424 d arranged to monitor fluid pressure in the fourth manifold conduit 462 d, a fifth pressure sensor 424 e arranged to monitor fluid pressure in the fifth manifold conduit 462 e, and a sixth pressure sensor 424 f arranged to monitor fluid pressure in the sixth manifold conduit 462 f. While not shown in FIG. 5 , the pressure sensors 424 a, 424 b, 424 c, 424 d, 424 e, 424 f are all electrically connected to the controller.

FIG. 6 illustrates another suspension system 600 that shares many of the same components as the suspension system 400 illustrated in FIGS. 4 and 5 , but in FIG. 6 different pump 610 and manifold assemblies 604 have been utilized. Rather than repeat the description set forth above, the following paragraphs describe the structure and function of the components in FIG. 6 that are new and/or different from those shown and described in connection with FIGS. 4 and 5 . It should be appreciated that the reference numbers in FIGS. 4 and 5 are “400” series numbers (e.g., 400, 402, 404, etc.) whereas the components in FIG. 6 that are the same or similar to the components of the suspension system 400 shown in FIGS. 4 and 5 share the same base reference numbers, but are listed as “600” series numbers (e.g., 600, 602, 604, etc.). Thus, the same description for element 400 above applies to element 600 in FIG. 6 and so on and so forth.

The pump assembly 606 illustrated in FIG. 6 includes a single direction pump 610 with an inlet port that is connected in fluid communication with the hydraulic reservoir 612 by a reservoir hydraulic line 618 and an outlet port that is connected to the pump hydraulic line 608. In operation, the single direction pump 610 draws in hydraulic fluid from the reservoir hydraulic line 618 via the inlet port and discharges hydraulic fluid into the pump hydraulic line 608 via the outlet port. As such, the single direction pump 610 produces a positive pressure in the pump hydraulic line 608 that can be used by manifold assembly 604 to increase fluid pressure in the suspension system 600. A check valve 678 is positioned in the pump hydraulic line 608 to prevent back feed when the single direction pump 610 is turned off. The pump assembly 606 also includes a return hydraulic line 680 that extends from the pump hydraulic line 108 to the hydraulic reservoir 612. A first pump valve 682 a is positioned in-line with the return hydraulic line 680. The pump assembly 606 also includes a pump bridge hydraulic line 683 that includes a second pump valve 682 b mounted in-line with the pump bridge hydraulic line 683. The pump bridge hydraulic line 683 connects to the pump hydraulic line 608 at a location between the single direct pump 610 and the check valve 678 and connects to the return hydraulic line 680 at a location between the first pump valve 682 a and the hydraulic reservoir 612. In accordance with this arrangement, fluid pressure in the pump hydraulic line 608 can be increased by turning on the pump 610 and closing the second pump valve 682 b and fluid pressure in the pump hydraulic line 608 can be decreased by turning the pump 610 off and opening the first pump valve 682 a.

In the example illustrated in FIG. 6 , only three manifold valves 622 a, 622 b, 622 c (i.e., the first manifold valve 622 a, the second manifold valve 622 b, and the third manifold valve 622 c) are connected in parallel with the pump hydraulic line 608. The fourth manifold valve 622 d is positioned between the first and second piston bores 666 a, 666 b and is arranged in fluid communication with the third manifold conduit 662 c on one side and the fourth manifold conduit 662 d on the other side. Thus, to increase fluid pressure in the fifth and/or sixth manifold conduits 662 e, 662 f independently of the first and second manifold conduits 662 a, 662 b, the third and fourth manifold valves 622 c, 622 d must be open while the pump 610 is running and the first and second manifold comfort valves 660 a, 660 b are closed to increase fluid pressure in the third and seventh piston chambers 674 c, 674 g, which urges the first and second floating pistons 668 a, 668 b to the right in FIG. 6 decreasing the volume of the fourth and eighth piston chambers 674 d, 674 h and increasing the pressure in the fourth and eighth piston chambers 674 d, 674 h.

FIG. 7 illustrates another suspension system 700 that shares many of the same components as the suspension system 400 illustrated in FIGS. 4 and 5 , but in FIG. 7 a different manifold assembly 704 has been utilized. Rather than repeat the description set forth above, the following paragraphs describe the structure and function of the components in FIG. 7 that are new and/or different from those shown and described in connection with FIGS. 4 and 5 . It should be appreciated that the reference numbers in FIGS. 4 and 5 are “400” series numbers (e.g., 400, 402, 404, etc.) whereas the components in FIG. 7 that are the same or similar to the components of the suspension system 400 shown in FIGS. 4 and 5 share the same base reference numbers, but are listed as “700” series numbers (e.g., 700, 702, 704, etc.). Thus, the same description for element 400 above applies to element 700 in FIG. 7 and so on and so forth.

The manifold assembly 704 illustrated in FIG. 7 has the same components and hydraulic arrangement as the manifold assembly 404 illustrated in FIGS. 4 and 5 , but in FIG. 7 the placement of the various components of the manifold assembly 704 is different to allow the manifold assembly 704 to be packaged in the front of the vehicle between the front dampers 702 a, 702 b. The manifold assembly 704 illustrated in FIG. 7 includes a front left sub-assembly 784 a and a front right sub-assembly 784 b. The front right sub-assembly 784 b includes the first piston bore 766 a, the first floating piston 768 a, the first manifold valve 722 a, the third manifold valve 722 c, the first manifold conduit 762 a, and the fifth manifold conduit 762 e. The front left sub-assembly 784 a includes the second piston bore 466 b, the second floating piston 768 b, the second manifold valve 722 b, the fourth manifold valve 722 d, the second manifold conduit 762 b, and the sixth manifold conduit 762 f. The pump hydraulic line 708 extends between the front left and front right sub-assemblies 784 a, 784 b and splits to connect to the manifold valves 722 a, 722 b, 722 c, 722 d on either side. The third and fourth manifold conduits 762 c, 762 d extend laterally between the front left and front right sub-assemblies 784 a, 784 b to connect the second and sixth piston chambers 774 b, 774 f and the third and seventh piston chambers 774 c, 774 g, respectively. It should be appreciated that the order and arrangement of the piston chambers 774 e, 774 f, 774 g, 774 h in the second piston bore 766 b shown in FIG. 7 is opposite from that shown in FIGS. 4 and 5 . In other words, in accordance with the arrangement shown in FIG. 7 , the first piston chamber 774 a (which is connected in fluid communication with the first manifold conduit 762 a) faces the fifth piston chamber 774 e (which is connection in fluid communication with the second manifold conduit 762 b). In other words, in FIG. 7 the fifth piston chamber 774 e (which is connection in fluid communication with the second manifold conduit 762 b) is to the right of the eighth piston chamber 774 h (which is connected in fluid communication with the sixth manifold conduit 762 f), whereas in FIGS. 4 and 5 the fifth piston chamber 474 e (which is connected in fluid communication with the second manifold conduit 462 b) is to the left of the eighth piston chamber 474 h (which is connected in fluid communication with the sixth manifold conduit 462 f). This reversal of the arrangement of the piston chambers 774 e, 774 f, 774 g, 774 h in the second piston bore 766 b simplifies and shortens the runs required for the manifold hydraulic lines 738 a, 738 b, 738 c, 738 d and is therefore advantageous.

Many other modifications and variations of the present disclosure are possible in light of the above teachings and may be practiced otherwise than as specifically described while within the scope of the appended claims. 

1. A suspension system, comprising: a front left damper including a first compression chamber and a first rebound chamber; a front right damper including a second compression chamber and a second rebound chamber; a back left damper including a third compression chamber and a third rebound chamber; a back right damper including a fourth compression chamber and a fourth rebound chamber; a first hydraulic circuit including a front hydraulic line, a rear hydraulic line, and a first longitudinal hydraulic line that extends between and fluidly connects said front and rear hydraulic lines of said first hydraulic circuit; said front hydraulic line of said first hydraulic circuit extending between and fluidly connecting said first longitudinal hydraulic line and said second rebound chamber of said front right damper; said rear hydraulic line of said first hydraulic circuit extending between and fluidly connecting said first longitudinal hydraulic line and said fourth rebound chamber of said back right damper; said first longitudinal hydraulic line extending between and fluidly connecting said first compression chamber of said front left damper and said third compression chamber of said back left damper; a second hydraulic circuit including a front hydraulic line, a rear hydraulic line, and a second longitudinal hydraulic line that extends between and fluidly connects said front and rear hydraulic lines of said second hydraulic circuit; said front hydraulic line of said second hydraulic circuit extending between and fluidly connecting said second longitudinal hydraulic line and said first rebound chamber of said front left damper; said rear hydraulic line of said second hydraulic circuit extending between and fluidly connecting said second longitudinal hydraulic line and said third rebound chamber of said back left damper; said second longitudinal hydraulic line extending between and fluidly connecting said second compression chamber of said front right damper and said fourth compression chamber of said back right damper; and a first longitudinal comfort valve positioned in said first longitudinal hydraulic line between said front and rear hydraulic lines of said first hydraulic circuit and a second longitudinal comfort valve positioned in said second longitudinal hydraulic line between said front and rear hydraulic lines of said second hydraulic circuit, said first and second longitudinal comfort valves being electromechanical valves that control fluid flow through said first and second longitudinal hydraulic lines.
 2. The suspension system as set forth in claim 1, further comprising: a front left bridge hydraulic line that extends between and fluidly connects said first longitudinal hydraulic line of said first hydraulic circuit and said front hydraulic line of said second hydraulic circuit; a front right bridge hydraulic line that extends between and fluidly connects said front hydraulic line of said first hydraulic circuit and said second longitudinal hydraulic line of said second hydraulic circuit; a back left bridge hydraulic line that extends between and fluidly connects said first longitudinal hydraulic line of said first hydraulic circuit and said rear hydraulic line of said second hydraulic circuit; and a back right bridge hydraulic line that extends between and fluidly connects said rear hydraulic line of said first hydraulic circuit and said second longitudinal hydraulic line of said second hydraulic circuit.
 3. The suspension system as set forth in claim 2, further comprising: a front left comfort valve that is positioned in and controls fluid flow through said front left bridge hydraulic line; a front right comfort valve that is positioned in and controls fluid flow through said front right bridge hydraulic line; a back left comfort valve that is positioned in and controls fluid flow through said back left bridge hydraulic line; and a back right comfort valve that is positioned in and controls fluid flow through said back right bridge hydraulic line.
 4. The suspension system as set forth in claim 3, wherein said front left comfort valve is an electromechanical valve that is configured to permit fluid flow between said first longitudinal hydraulic line of said first hydraulic circuit and said front hydraulic line of said second hydraulic circuit in an open position and block fluid flow between said first longitudinal hydraulic line of said first hydraulic circuit and said front hydraulic line of said second hydraulic circuit in a closed position.
 5. The suspension system as set forth in claim 3, wherein said front right comfort valve is an electromechanical valve that is configured to permit fluid flow between said front hydraulic line of said first hydraulic circuit and said second longitudinal hydraulic line of said second hydraulic circuit in an open position and block fluid flow between said front hydraulic line of said first hydraulic circuit and said second longitudinal hydraulic line of said second hydraulic circuit in a closed position.
 6. The suspension system as set forth in claim 3, wherein said back left comfort valve is an electromechanical valve that is configured to permit fluid flow between said first longitudinal hydraulic line of said first hydraulic circuit and said rear hydraulic line of said second hydraulic circuit in an open position and block fluid flow between said first longitudinal hydraulic line of said first hydraulic circuit and said rear hydraulic line of said second hydraulic circuit in a closed position.
 7. The suspension system as set forth in claim 3, wherein said back right comfort valve is an electromechanical valve that is configured to permit fluid flow between said rear hydraulic line of said first hydraulic circuit and said second longitudinal hydraulic line of said second hydraulic circuit in an open position and block fluid flow between said rear hydraulic line of said first hydraulic circuit and said second longitudinal hydraulic line of said second hydraulic circuit in a closed position.
 8. The suspension system as set forth in claim 1, wherein said first longitudinal comfort valve is actuatable between open and closed positions such that said first longitudinal comfort valve is configured to permit fluid flow through said first longitudinal hydraulic line between said first compression chamber of said front left damper, said third compression chamber of said back left damper, and said fourth rebound chamber of said back right damper in said open position and block fluid flow through said first longitudinal hydraulic line between said first compression chamber of said front left damper, said third compression chamber of said back left damper, and said fourth rebound chamber of said back right damper in said closed position.
 9. The suspension system as set forth in claim 1, wherein said second longitudinal comfort valve is actuatable between open and closed positions such that said second longitudinal comfort valve is configured to permit fluid flow through said second longitudinal hydraulic line between said second compression chamber of said front right damper, said third rebound chamber of said back left damper, and said fourth compression chamber of said back right damper in said open position and block fluid flow through said second longitudinal hydraulic line between said second compression chamber of said front right damper, said third rebound chamber of said back left damper, and said fourth compression chamber of said back right damper in said closed position.
 10. A suspension system, comprising: a front left damper including a first compression chamber that is arranged in fluid communication with a first compression chamber port and a first rebound chamber that is arranged in fluid communication with a first rebound chamber port; a front right damper including a second compression chamber that is arranged in fluid communication with a second compression chamber port and a second rebound chamber that is arranged in fluid communication with a second rebound chamber port; a back left damper including a third compression chamber that is arranged in fluid communication with a third compression chamber port and a third rebound chamber that is arranged in fluid communication with a third rebound chamber port; a back right damper including a fourth compression chamber that is arranged in fluid communication with a fourth compression chamber port and a fourth rebound chamber that is arranged in fluid communication with a third rebound chamber port; a first hydraulic circuit including a front hydraulic line, a rear hydraulic line, and a first longitudinal hydraulic line that extends between and fluidly connects said front and rear hydraulic lines of said first hydraulic circuit; said front hydraulic line of said first hydraulic circuit extending between and fluidly connecting said first longitudinal hydraulic line and said second rebound chamber port of said front right damper; said rear hydraulic line of said first hydraulic circuit extending between and fluidly connecting said first longitudinal hydraulic line and said fourth rebound chamber port of said back right damper; said first longitudinal hydraulic line extending between and fluidly connecting said first compression chamber port of said front left damper and said third compression chamber port of said back left damper; a second hydraulic circuit including a front hydraulic line, a rear hydraulic line, and a second longitudinal hydraulic line that extends between and fluidly connects said front and rear hydraulic lines of said second hydraulic circuit; said front hydraulic line of said second hydraulic circuit extending between and fluidly connecting said second longitudinal hydraulic line and said first rebound chamber port of said front left damper; said rear hydraulic line of said second hydraulic circuit extending between and fluidly connecting said second longitudinal hydraulic line and said third rebound chamber port of said back left damper; said second longitudinal hydraulic line extending between and fluidly connecting said second compression chamber port of said front right damper and said fourth compression chamber port of said back right damper; and a first longitudinal comfort valve positioned in said first longitudinal hydraulic line between said front and rear hydraulic lines of said first hydraulic circuit and a second longitudinal comfort valve positioned in said second longitudinal hydraulic line between said front and rear hydraulic lines of said second hydraulic circuit, said first and second longitudinal comfort valves being electromechanical valves.
 11. The suspension system as set forth in claim 10, wherein each of said rebound and compression ports includes a dampening valve.
 12. The suspension system as set forth in claim 11, wherein said dampening valves are spring-biased mechanical valves that are configured to set a rebound dampening rate and a compression dampening rate for each of said dampers.
 13. The suspension system as set forth in claim 11, wherein said dampening valves are electromechanical valves that are configured to set a rebound dampening rate and a compression dampening rate for each of said dampers.
 14. The suspension system as set forth in claim 10, wherein said first longitudinal comfort valve is actuatable between open and closed positions such that said first longitudinal comfort valve is configured to permit fluid flow through said first longitudinal hydraulic line between said front and rear hydraulic lines of said first hydraulic circuit in said open position and block fluid flow through said first longitudinal hydraulic line between said front and rear hydraulic lines of said first hydraulic circuit in said closed position.
 15. The suspension system as set forth in claim 10, wherein said second longitudinal comfort valve is actuatable between open and closed positions such that said second longitudinal comfort valve is configured to permit fluid flow through said second longitudinal hydraulic line between said front and rear hydraulic lines of said second hydraulic circuit in said open position and block fluid flow through said second longitudinal hydraulic line between said front and rear hydraulic lines of said second hydraulic circuit in said closed position.
 16. A suspension system, comprising: a front left damper including a first compression chamber and a first rebound chamber; a front right damper including a second compression chamber and a second rebound chamber; a back left damper including a third compression chamber and a third rebound chamber; a back right damper including a fourth compression chamber and a fourth rebound chamber; a pump assembly that includes a bi-directional pump; a manifold assembly with first and second manifold valves that are arranged in fluid communication with said pump assembly by a pump hydraulic line, said first and second manifold valves being electromechanical valves; a first hydraulic circuit including a front hydraulic line, a rear hydraulic line, a first longitudinal hydraulic line that extends between and fluidly connects said front and rear hydraulic lines of said first hydraulic circuit, and a first manifold hydraulic line that extends between and fluidly connects said first longitudinal hydraulic line and said first manifold valve; said front hydraulic line of said first hydraulic circuit extending between and fluidly connecting said first longitudinal hydraulic line and said second rebound chamber of said front right damper; said rear hydraulic line of said first hydraulic circuit extending between and fluidly connecting said first longitudinal hydraulic line and said fourth rebound chamber of said back right damper; said first longitudinal hydraulic line extending between and fluidly connecting said first compression chamber of said front left damper and said third compression chamber of said back left damper; a second hydraulic circuit including a front hydraulic line, a rear hydraulic line, a second longitudinal hydraulic line that extends between and fluidly connects said front and rear hydraulic lines of said second hydraulic circuit, and a second manifold hydraulic line that extends between and fluidly connects said second longitudinal hydraulic line and said second manifold valve; said front hydraulic line of said second hydraulic circuit extending between and fluidly connecting said second longitudinal hydraulic line and said first rebound chamber of said front left damper; said rear hydraulic line of said second hydraulic circuit extending between and fluidly connecting said second longitudinal hydraulic line and said third rebound chamber of said back left damper; said second longitudinal hydraulic line extending between and fluidly connecting said second compression chamber of said front right damper and said fourth compression chamber of said back right damper; and a first longitudinal comfort valve positioned in said first longitudinal hydraulic line between said front and rear hydraulic lines of said first hydraulic circuit and a second longitudinal comfort valve positioned in said second longitudinal hydraulic line between said front and rear hydraulic lines of said second hydraulic circuit, said first and second longitudinal comfort valves being electromechanical valves that control fluid flow through said first and second longitudinal hydraulic lines.
 17. The suspension system as set forth in claim 16, wherein said manifold assembly further includes a third manifold valve that is connected in fluid communication with said pump hydraulic line.
 18. The suspension system as set forth in claim 17, wherein said front left damper includes a front left lifter and said front right damper includes a front right lifter and wherein said front left and front right lifters are connected in fluid communication with said third manifold and are axially expandable to provide a front axle lift in response to an increase in fluid pressure inside said front left and front right lifters.
 19. The suspension system as set forth in claim 18, wherein said manifold assembly further includes a fourth manifold valve that is connected in fluid communication with said pump hydraulic line.
 20. The suspension system as set forth in claim 19, wherein said back left damper includes a back left lifter and said back right damper includes a back right lifter and wherein said back left and back right lifters are connected in fluid communication with said fourth manifold and are axially expandable to provide a rear axle lift in response to an increase in fluid pressure inside said back left and back right lifters. 